Abstract

This study used a four-axis computer controlled machine to determine the cutting forces (Cf), specific cutting energy (Sc) and specific energy (Se) affecting the processability of natural rocks. A total of 17 types of natural rocks were categorized according to their geological formations. This study consisted of three parts: (1) experimental measurement of the Cf resulting from processing natural rocks using a 6.0-mm diameter end mill cutting tool and a four-axis machine; (2) calculation of Cf, Sc and Se values; and (3) statistical analysis of the parameters. In terms of Cf, Sc and Se values, a statistically significant difference (P < 0.001) was observed among a depth of cut (dp) and feed speed (Va). It was found that the parameters that affected the processability of natural rocks were dp and Va. Accordingly, the processability of natural rocks processing type, dp and Va was found that affected. Simple linear regression was performed to examine the relationship between physicomechanical properties, and between Cf, Se and Sc values. As a result, regression equations were developed in consideration of the physicomechanical properties of natural rocks and the Cf, Sc and Se equation for the prediction of the efficiency of computer numerical control (CNC) machines.

Keywords: natural rock, CNC machine, efficiency, Cf, Sc, Se

## 1. Introduction

Natural stone industry is one of the most effective actors of the Turkish mining industry economy. With its 4000-year history of natural stone production, Turkey is one of the oldest natural stone producers in the world. Natural stones are classified as metamorphic, sedimentary and magmatic according to their formations [1]. Marble is a metamorphic rock formed by recrystallization of limestone. Marble is a metamorphic stone composed of calcite (CaCO3) and formed as a result of the recrystallization of the limestone under excessive pressure and heat [2–6]. CNC machines are electromechanical systems that process the materials according to the logical operation unit of numerical control (NC) codes defined by numbers, letters, and symbols of a product designed using a computer-aided design and manufacturing (CAD/CAM) program. Nowadays, 3D design in the natural stone industry can be processed with high accuracy, precision series and quality the use of CNC machine [7, 8]. Various processing technologies are used at natural stone quarries and factories to manufacture as building materials. In quarries, in the production of natural stone blocks, diamond wire cutting and chain arm cutting machines are widely used in factories, plates and panels manufacturing in the production of block cutter ST and gangsaw machines [9–18].

CNC machine is used to process natural stone blocks and wastes in 3D design products to be used in buildings. Many studies have been found on the Cf in circular saws depending on the physicomechanical properties of natural rocks, modeling of the Se and socket [19–23], the definition of the theoretical chip geometry [24], and connections between tangential cutting force and chip thickness [25–27]. Some other studies address the effect of processing parameters on tool wear [28–31], the modeling of natural stone cutting with diamond cutting tools [32] and specific grinding energy of chip samples under a scanning microscope [33] in order to determine specific cutting energy and power consumption [34, 35]. Energy and the type of cutting mechanism used in the production of end products from natural rocks lead to the wear of cutting tools. Energy consumption and wear of cutting edges are the important factors affecting processing costs. These factors should be efficiently to reduce processing costs. It is therefore important to determine the cutting performance of natural rocks according to their characteristics. Cut tools should be selected carefully and performance forecast should be proper in order to improve the processing efficiency of natural rocks and reduce costs. Different from the manufacture of plates and panels in which gangsaw and cutter ST are deep cut on the x (length), z (depth) axis, this process requires few depth cut and precision tools with a CNC machine on the x (length), y (width) and z (depth) axis. Cf, Sc and wear of diamond cut tools have a low spindle and Va in the processability of rocks in the CNC machine with internally cooled cut tools. Carbide coated end mills tools are widely used in the natural stones sectors. In addition, the number of studies on parameters affecting the processability of natural rocks in the CNC machine is less [36–40].

Cut tool (carbide-coated end-mill cutting edge tool) was used in the processing of natural rocks by CNC machine. Figure 1 shows the image of the end mill cut tool.

Main modal compositions

Travertine T1-T5 Sedimentary Calcite 300 300 30 15 Polished Marble M1-M7 Metamorphic Calcite 300 300 30 15 Polished Limestone K1-K5 Sedimentary Calcite 300 300 30 15 Polished

Dimensions (mm)

N Surface processing

Figure 2 shows that the CNC consists of the machine, electric motors, pneu-

A 4-Axis CNC (Megatron) machine designed for the natural stone industry in Afyon Kocatepe University Natural Stone Processing Laboratory was used for the

Processability tests were performed on natural rocks according to the dp and Va cutting parameters by using CNC machine. Alpha CAM drawing program was used

120 25 mm in size 18 rectangular samples were produced using a 3D modeling and

Technical properties Unit Values Code — MFR-6 Cutting tool diameter/d1 mm 6 Stem diameter/d2 mm 6 Cutting length/l2 mm 25 End length/l1 mm 76 Milling end — 36,677 Edge number — 4 Helix angle (°) 25

A power meter, also known as load meter, built in the CNC machine was used in the processability tests. This testing tool consists of a measurement unit, a load cell,

to determine the cutting parameters of natural rocks. As shown in Figure 3,

Table 2 shows the technical specifications of the end mill cut tool.

matic or hydraulic power units, control panel and software.

Pertographic name

Force and Specific Energy in Natural Rocks Cutting by Four-Axis Machine

Characteristics of natural rocks used in experimental tests.

simulation program for the processability tests.

a controller unit and Defne Lab Soft program (Figure 4).

tests. The technical features of the machine are given in Table 3.

2.2 Method

Figure 1.

Table 2.

13

Image of the end mill cutting edge tool.

Technical properties of end-mill cutting edge tool.

Table 1.

Natural rocks

Sample code

DOI: http://dx.doi.org/10.5772/intechopen.85622

This study investigated the relationship between the values of the Cf, Se and Sc obtained from the processing of rocks using CNC, and related parameters (i.e., cutting parameters and physicomechanical properties). Cf, Se and Sc values depending on the dp and Va of natural rocks have been analyzed (ANOVA) statistically. Results show that 1.0, 1.2 and 1.6 mm at the dp and 2000, 2500, 3000 mm/ min at the Va are important cutting parameters in the processability of natural rocks. Regression models were developed for the estimation of Cf, Se and Sc of the with measured by power and load meter tester. Regression analyses were performed to determine the optimum relationship between the Cf, Se and Sc dependent variable and physicomechanical properties independent variable in three different groups of natural rocks. Regression models developed in this study can be used by planners and natural stone manufacturing companies for cost analysis and mill cut tool processing programs in natural rocks. We recommend that it be considered in further studies use a larger database to analyze the possibility of regression analyses the Cf, Se and Sc any of the physico-mechanical parameters of natural rocks.
